Maybe it's just personal preference - or possibly some sites are more awkward, but posts to Pinterest I have always done manually through their own site.
This is my own preference but I have usually gone on and looked and pinned other people's pins, as well as pinning my own posts. I enjoy spending 5-10 minutes reviewing other people's content and seeing if there are ideas for myself.
I also post manually to Google+ because I like to select which community would be best suited to the post and again it's an opportunity to like or share other posts.
Instagram doesn't take post links they prefer original visual content so it's great for sites that produce their own photos or short video because these can be uploaded directly to the site.
Using A Social Media Plugin
One of the easiest ways to share content manually is to use a social media plugin such as SumoMe.
This is the one with the social share buttons down the side of your post. The plugin will also show you how many people have shared your content, and to which sites.
Flipboard and Google+ (if I am posting to my own collection) are easily done this way.
All of this might seem very time intensive, but then they do say you should spend more time marketing your content than writing it.
Finally don't forget to make full use of your mobile phone to help manage social media, as I'll now show you....